net/ax25/ax25_subr.c

   1 /*
   2  * This program is free software; you can redistribute it and/or modify
   3  * it under the terms of the GNU General Public License as published by
   4  * the Free Software Foundation; either version 2 of the License, or
   5  * (at your option) any later version.
   6  *
   7  * Copyright (C) Alan Cox GW4PTS (alan@lxorguk.ukuu.org.uk)
   8  * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
   9  * Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de)
  10  * Copyright (C) Frederic Rible F1OAT (frible@teaser.fr)
  11  */
  12 #include <linux/errno.h>
  13 #include <linux/types.h>
  14 #include <linux/socket.h>
  15 #include <linux/in.h>
  16 #include <linux/kernel.h>
  17 #include <linux/timer.h>
  18 #include <linux/string.h>
  19 #include <linux/sockios.h>
  20 #include <linux/net.h>
  21 #include <net/ax25.h>
  22 #include <linux/inet.h>
  23 #include <linux/netdevice.h>
  24 #include <linux/skbuff.h>
  25 #include <net/sock.h>
  26 #include <net/tcp_states.h>
  27 #include <asm/uaccess.h>
  28 #include <asm/system.h>
  29 #include <linux/fcntl.h>
  30 #include <linux/mm.h>
  31 #include <linux/interrupt.h>
  32
  33 /*
  34  *      This routine purges all the queues of frames.
  35  */
  36 void ax25_clear_queues(ax25_cb *ax25)
  37 {
  38         skb_queue_purge(&ax25->write_queue);
  39         skb_queue_purge(&ax25->ack_queue);
  40         skb_queue_purge(&ax25->reseq_queue);
  41         skb_queue_purge(&ax25->frag_queue);
  42 }
  43
  44 /*
  45  * This routine purges the input queue of those frames that have been
  46  * acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
  47  * SDL diagram.
  48  */
  49 void ax25_frames_acked(ax25_cb *ax25, unsigned short nr)
  50 {
  51         struct sk_buff *skb;
  52
  53         /*
  54          * Remove all the ack-ed frames from the ack queue.
  55          */
  56         if (ax25->va != nr) {
  57                 while (skb_peek(&ax25->ack_queue) != NULL && ax25->va != nr) {
  58                         skb = skb_dequeue(&ax25->ack_queue);
  59                         kfree_skb(skb);
  60                         ax25->va = (ax25->va + 1) % ax25->modulus;
  61                 }
  62         }
  63 }
  64
  65 void ax25_requeue_frames(ax25_cb *ax25)
  66 {
  67         struct sk_buff *skb;
  68
  69         /*
  70          * Requeue all the un-ack-ed frames on the output queue to be picked
  71          * up by ax25_kick called from the timer. This arrangement handles the
  72          * possibility of an empty output queue.
  73          */
  74         while ((skb = skb_dequeue_tail(&ax25->ack_queue)) != NULL)
  75                 skb_queue_head(&ax25->write_queue, skb);
  76 }
  77
  78 /*
  79  *      Validate that the value of nr is between va and vs. Return true or
  80  *      false for testing.
  81  */
  82 int ax25_validate_nr(ax25_cb *ax25, unsigned short nr)
  83 {
  84         unsigned short vc = ax25->va;
  85
  86         while (vc != ax25->vs) {
  87                 if (nr == vc) return 1;
  88                 vc = (vc + 1) % ax25->modulus;
  89         }
  90
  91         if (nr == ax25->vs) return 1;
  92
  93         return 0;
  94 }
  95
  96 /*
  97  *      This routine is the centralised routine for parsing the control
  98  *      information for the different frame formats.
  99  */
 100 int ax25_decode(ax25_cb *ax25, struct sk_buff *skb, int *ns, int *nr, int *pf)
 101 {
 102         unsigned char *frame;
 103         int frametype = AX25_ILLEGAL;
 104
 105         frame = skb->data;
 106         *ns = *nr = *pf = 0;
 107
 108         if (ax25->modulus == AX25_MODULUS) {
 109                 if ((frame[0] & AX25_S) == 0) {
 110                         frametype = AX25_I;                     /* I frame - carries NR/NS/PF */
 111                         *ns = (frame[0] >> 1) & 0x07;
 112                         *nr = (frame[0] >> 5) & 0x07;
 113                         *pf = frame[0] & AX25_PF;
 114                 } else if ((frame[0] & AX25_U) == 1) {  /* S frame - take out PF/NR */
 115                         frametype = frame[0] & 0x0F;
 116                         *nr = (frame[0] >> 5) & 0x07;
 117                         *pf = frame[0] & AX25_PF;
 118                 } else if ((frame[0] & AX25_U) == 3) {  /* U frame - take out PF */
 119                         frametype = frame[0] & ~AX25_PF;
 120                         *pf = frame[0] & AX25_PF;
 121                 }
 122                 skb_pull(skb, 1);
 123         } else {
 124                 if ((frame[0] & AX25_S) == 0) {
 125                         frametype = AX25_I;                     /* I frame - carries NR/NS/PF */
 126                         *ns = (frame[0] >> 1) & 0x7F;
 127                         *nr = (frame[1] >> 1) & 0x7F;
 128                         *pf = frame[1] & AX25_EPF;
 129                         skb_pull(skb, 2);
 130                 } else if ((frame[0] & AX25_U) == 1) {  /* S frame - take out PF/NR */
 131                         frametype = frame[0] & 0x0F;
 132                         *nr = (frame[1] >> 1) & 0x7F;
 133                         *pf = frame[1] & AX25_EPF;
 134                         skb_pull(skb, 2);
 135                 } else if ((frame[0] & AX25_U) == 3) {  /* U frame - take out PF */
 136                         frametype = frame[0] & ~AX25_PF;
 137                         *pf = frame[0] & AX25_PF;
 138                         skb_pull(skb, 1);
 139                 }
 140         }
 141
 142         return frametype;
 143 }
 144
 145 /*
 146  *      This routine is called when the HDLC layer internally  generates a
 147  *      command or  response  for  the remote machine ( eg. RR, UA etc. ).
 148  *      Only supervisory or unnumbered frames are processed.
 149  */
 150 void ax25_send_control(ax25_cb *ax25, int frametype, int poll_bit, int type)
 151 {
 152         struct sk_buff *skb;
 153         unsigned char  *dptr;
 154
 155         if ((skb = alloc_skb(ax25->ax25_dev->dev->hard_header_len + 2, GFP_ATOMIC)) == NULL)
 156                 return;
 157
 158         skb_reserve(skb, ax25->ax25_dev->dev->hard_header_len);
 159
 160         skb_reset_network_header(skb);
 161
 162         /* Assume a response - address structure for DTE */
 163         if (ax25->modulus == AX25_MODULUS) {
 164                 dptr = skb_put(skb, 1);
 165                 *dptr = frametype;
 166                 *dptr |= (poll_bit) ? AX25_PF : 0;
 167                 if ((frametype & AX25_U) == AX25_S)             /* S frames carry NR */
 168                         *dptr |= (ax25->vr << 5);
 169         } else {
 170                 if ((frametype & AX25_U) == AX25_U) {
 171                         dptr = skb_put(skb, 1);
 172                         *dptr = frametype;
 173                         *dptr |= (poll_bit) ? AX25_PF : 0;
 174                 } else {
 175                         dptr = skb_put(skb, 2);
 176                         dptr[0] = frametype;
 177                         dptr[1] = (ax25->vr << 1);
 178                         dptr[1] |= (poll_bit) ? AX25_EPF : 0;
 179                 }
 180         }
 181
 182         ax25_transmit_buffer(ax25, skb, type);
 183 }
 184
 185 /*
 186  *      Send a 'DM' to an unknown connection attempt, or an invalid caller.
 187  *
 188  *      Note: src here is the sender, thus it's the target of the DM
 189  */
 190 void ax25_return_dm(struct net_device *dev, ax25_address *src, ax25_address *dest, ax25_digi *digi)
 191 {
 192         struct sk_buff *skb;
 193         char *dptr;
 194         ax25_digi retdigi;
 195
 196         if (dev == NULL)
 197                 return;
 198
 199         if ((skb = alloc_skb(dev->hard_header_len + 1, GFP_ATOMIC)) == NULL)
 200                 return; /* Next SABM will get DM'd */
 201
 202         skb_reserve(skb, dev->hard_header_len);
 203         skb_reset_network_header(skb);
 204
 205         ax25_digi_invert(digi, &retdigi);
 206
 207         dptr = skb_put(skb, 1);
 208
 209         *dptr = AX25_DM | AX25_PF;
 210
 211         /*
 212          *      Do the address ourselves
 213          */
 214         dptr  = skb_push(skb, ax25_addr_size(digi));
 215         dptr += ax25_addr_build(dptr, dest, src, &retdigi, AX25_RESPONSE, AX25_MODULUS);
 216
 217         ax25_queue_xmit(skb, dev);
 218 }
 219
 220 /*
 221  *      Exponential backoff for AX.25
 222  */
 223 void ax25_calculate_t1(ax25_cb *ax25)
 224 {
 225         int n, t = 2;
 226
 227         switch (ax25->backoff) {
 228         case 0:
 229                 break;
 230
 231         case 1:
 232                 t += 2 * ax25->n2count;
 233                 break;
 234
 235         case 2:
 236                 for (n = 0; n < ax25->n2count; n++)
 237                         t *= 2;
 238                 if (t > 8) t = 8;
 239                 break;
 240         }
 241
 242         ax25->t1 = t * ax25->rtt;
 243 }
 244
 245 /*
 246  *      Calculate the Round Trip Time
 247  */
 248 void ax25_calculate_rtt(ax25_cb *ax25)
 249 {
 250         if (ax25->backoff == 0)
 251                 return;
 252
 253         if (ax25_t1timer_running(ax25) && ax25->n2count == 0)
 254                 ax25->rtt = (9 * ax25->rtt + ax25->t1 - ax25_display_timer(&ax25->t1timer)) / 10;
 255
 256         if (ax25->rtt < AX25_T1CLAMPLO)
 257                 ax25->rtt = AX25_T1CLAMPLO;
 258
 259         if (ax25->rtt > AX25_T1CLAMPHI)
 260                 ax25->rtt = AX25_T1CLAMPHI;
 261 }
 262
 263 void ax25_disconnect(ax25_cb *ax25, int reason)
 264 {
 265         ax25_clear_queues(ax25);
 266
 267         ax25_stop_t1timer(ax25);
 268         ax25_stop_t2timer(ax25);
 269         ax25_stop_t3timer(ax25);
 270         ax25_stop_idletimer(ax25);
 271
 272         ax25->state = AX25_STATE_0;
 273
 274         ax25_link_failed(ax25, reason);
 275
 276         if (ax25->sk != NULL) {
 277                 local_bh_disable();
 278                 bh_lock_sock(ax25->sk);
 279                 ax25->sk->sk_state     = TCP_CLOSE;
 280                 ax25->sk->sk_err       = reason;
 281                 ax25->sk->sk_shutdown |= SEND_SHUTDOWN;
 282                 if (!sock_flag(ax25->sk, SOCK_DEAD)) {
 283                         ax25->sk->sk_state_change(ax25->sk);
 284                         sock_set_flag(ax25->sk, SOCK_DEAD);
 285                 }
 286                 bh_unlock_sock(ax25->sk);
 287                 local_bh_enable();
 288         }
 289 }